ML20091M864

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Verification Analysis for Computer Program
ML20091M864
Person / Time
Site: Byron, Braidwood  Constellation icon.png
Issue date: 08/25/1995
From:
MPR ASSOCIATES, INC.
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Shared Package
ML20091M806 List:
References
PROC-950825, NUDOCS 9508300320
Download: ML20091M864 (48)
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c f B.1 Introduction To check the results obtained from the transient thermal. hydraulic computer program, several test problems which have' analytic solutions or allow comparison to experimental data were run using the These test problems were chosen to check \\ program. those features of the program which were considered _ auxiliary feed pump important for the Important parameters for this turbine piping analysis. analysis were considered to be as follows: The conduction of heat to the pipe wall from the 1. l fluid which is responsible for the condensation of i steam. The heat transfer coefficient between the pipe 2. This coefficient includes wall and the fluid. regions of free convection, forced convection, and condensation heat transfer. a The slip model which determines the rata at which 4 3. separation of water and steam occur in the The time at which the water accumulates piping. i i B.2

~- ~ ct th3 inlSt to tho turbinDo 10 dep;ndsnt on thic model although the total water available would probably not be very sensitive to this parameter. The conservation of mass, momentum, and energy as 4. solved by the program including the appropriate equations of state. i Conduction B.2 Comparison to Analytic Solution of Heat Throuch a Cylindrical Wall _ Figure B1 shcws the computer model which was used to obtain the solution for the transient conduction heat t transfer through a cylindrical wall similar to that which exists in the _ auxiliary feed pump i turbine piping. The pipe wall was assumed to be at an initial uniform temperature of 100 degrees Fahrenheit 0.2 and a constant heat transfer coefficient of r was assumed for the inside surface Btu /sec/sq f t/deg F of the wall with the fluid temperature at 500 degrees F ahrenheit. The outside wall of the pipe was considered perfectly insulated. The solution obtained 4 assuming using the thermal hydraulic computer program, several different numbers of elements through the pipe is compared to an analytic solution for this

wall, problem in Figure B2.- The comparison indicates that the thermal hydraulic computer program provides B.3 1

1 z \\ l i racconnble antwara to thic probica and that tha pipa wall can be adequately modeled by four elements across its thickness. l 1 i B.3 Reasonableness of Heat Transfer Coefficients The thermal hydraulic computer program used for this analysis provides as part of the print-out the equivalent heat transfer coefficient for each heat flow path.. The~ magnitude of the heat transfer coefficients were checked for reasonableness against hand calculations and published results. B.4 Comparison to Test Data From Reference 3 Reference 3 provides measured results of void fraction and vessel pressure for a test vessel ~which was partially filled with saturated water at high pressure and then blown down through an orifice. The configuration of the test vessel is shown in figure 83 as it appears in Reference 3. As the vessel depressurizes, the saturated water inside the vessel flashes into steam. The void fraction as a function of height in the vessel at different pressures during the blowdown provides a good test for the effect of slip between water and steam as the steam tries to escape from the vessel. Figure B4 compares the measured void B.4 1

fraction ac -provided in Rotoranco 3 ct 10 socrnda end at 40 seconds after initiation of the blowdown to those which were calculated by the thermal hydraulic computer program used to analyze the,_, ,_ auxiliary feed pump steam supply piping. The comparison shows that the slip model in the computer program is adequate to determine qualitatively the separation of steam and water which would have occurred during the June 9th 1 transient at Figure B5 compares the rate of depressurization from Reference 3 to that calculated by the thermal hydraulic program used to analyze the ._ Auxiliary Feed Pump Turbine steam supply piping. The ccmparison indicates that a slightly more rapid depressurization is calculated than was measured; howe ve r, for both the pressure rate of change and the void fraction distribution, the agreement with the measured data is considered good. The lower calculated value for the pressure at 40 seconds is consistent with the higher void fraction which is calculated for that time. G I B.5 (

Analysin of a Plo7 Comprancion Wnve U.5 l As a final check on results obtained from the therma hydraulic computer program, a long pipe at high pressure and closed at one end was analyzed for the effect of a sudden increase in pressure at the open Superheated steam was used as the medium boundary. The analytic solution of this problem

i. side the pipe.

t requires-that the shock front travel down the p,ipe at l d end the speed of sound and is reflected from the c ose The speed of sound is twice its original magnitude. at t not an input to the thermal hydraulic program and mus i be obtained from the solution of the fluid conserva d by equations combined with the equations of state use Consequently, the solution to this j the program. id problem is considered to be a good test of the flu dynamics as they are solved for the Davis-Besse June i ^ 9th transient particularly since opening the steam l __ auxiliary feed pump admission valves in the _,, h steam piping (which admits high pressure steam from t e generators into the low pressure region of the i h f auxiliary feed pump steam piping to pressurize t e is similar in nature to the sudden piping) l d for preswurization of one end of the pipe as ana yze The configuration used for the test this problem. problem is shown in Figure B6. I i B.6 i l

Rsculto from the tect problem cra chown in Figuro B7 These results indicate that the -wave front which forms due to the sudden pressurization holds its shape and travels at a speed of about 1950 feet per second once it has diffused over a few control voinmes. The speed of sound for superheated steam at 500 psia and 600 3 degrees Fahrenheit is given as 1860 feet per second in Reference 4. The reflected wave from the closed and of I the pipe also behaves as expected. Consequently, the effect of the much slower pressurization which occurs , hen the valves in the feed pump turbine at w i steam supply piping are opened on a slow ramp in time should be determined adequately by the thermal hydraulic computer program used for this analysis. i e i f B.7 4 'Y

,r i 0.22" Pipe Wall-l Outside Insulated . Initial' Wall Temperature 100 Degrees Fahrenheit- , p n a + 2 l 0.2 Stu/sec/ft /dag F j Beat Transfer Coefficient with 500 degree l T2.uid Temperature i 6"_O. D. ~ Plag,Qgn @ g, b l 0 r 4 i 2 Conductivity:.0022 Stu/sec/ft /deg F Heat Capacity:.12 Btu /lb/deg F 3 Density: 490 lbs/ft l i FIGURE B1 Schematic of Pipe Used for Thermal Conduction Problem

600 Analytic 20 Elements a 4 Eleznents 500 400 Solution at [ 5 seconds 300 Solution at 200 100 Initial Condition 0 0.0 0.25 0.5 0.75 1.0 Fraction of Pipe Wall FIGURE B2 Solution for Heat Conduction Through Pipe Wal3.

computer-Model Test configuratica A Blowdown 14 15 Orifice u i 13 noundary 8 0 at l 12 Atmospheric Conditions 11-10 9 =:_-. 8 14 feet i 7 ~ 6 1 Blowdown 5 ,j -+ 1 foot +- Valve 4 [ F q 3 ~ Suppreseior 2 ~ ~ f 1 4 FIGURE B3 d' Test Configuration from Reference 3 and Computer Model c 4. m

.At 40 Seconds' ~At 10. Seconds ss- .a Measured 1.0 ~ .p ' Measured x Calculated . Calculated p .8- .8 6 . void Fraction.6 l D = i .4 r O .4 y [ p y s ~ ,0* O l De v i U" # D .2 I ,0* a .2 Y F~ ? 0 e i t i i i 0 2 4 6 8 10 12 14 0 2. 4 6 8 10 12 14 0 e i Axial Distance in feet i Axial Distance in feet frosa Bottom. A from Bottom FIGURE B4 Comparison of Calculated and Measured Voida for Test from Reference 3

l P 1000 900 Measured Calculated 800 3 00 Pressure (PSI) 600 500 3 400 J l 300 g J 200 L 100 t l 0 0 50 100 150 200 250 300 Time (seconds) i I r i ^ t FIGURE B5 Comparison between Measured and Calculated Pressure for Test from Reference 3 i i 2

2 feet Pipe Diameter: 500 psia Initial Pressure: 600 F 0 Initial Temperature: Closed at End Prassure Boundary at 600 paia 100 feet D FIGURE B6 Geometry Used for Pressurized Pipe Test Problem t

- 800 a I t 800 Initial conditions Pipe are 500 psia at.0593 seconds and 6000P superhea( steam - 600 600 - / [ Pressure (paia) at.0193 seconds at 0393 - 400 400, seconds at 0073 seconds - 200 200 - _0 i s 0 _,l I 0 20 40 60 80 100 i FIGURE B7-t Pressure Distribution at Various Times for Pipe Pressurized at End

' Enclosme 3 Paper Presented to ASMPJFRK Power Generadon Conference i 4 i

^""" "** In the connector represesting the pump is modified accirdingly, le the second case, for example after a pump trip occurs. the esestdeun of the p e p depends K\\\\\\\\ N en the interaction of the peep with the fluid and a dynamic torque belance en the pump shaft. -In the / e second case. the seletion of egustions in addition to. t d to / . the fluid dynamic equations will be reeu re represent the peep behavior. The rate of change of \\ F "'", + tile speed of the pump is given by the terque divided by the retary inertia of he pung shaft assembly. 4 t (12) w= I

  • e

= t :is the tiet torque on the pump where: 1 is the rotary taertta of the pump shaft assembly l ' The not torque on the pump Includes the torque due to f the pump motor, the torgue app 11ed by the fluid, torque from losses in the bearings, and torque due te. \\ ' losses from the fluid. . aus (13) i t.= t,- tr th-tf1 f!GURE 2 is the torque applied by the mocor Typical Check Valve Geometry } where: t, W tf ' = AP p is the fluid torque e is the angle of the disk I where: t is the not torque on the disk assembly ' J Prof w I 1 is the rotary inertia of the disk "I - (88-I tb b "' ref cef The net torque tending to rotate the disk includes the fluid forces, the buoyant weight of the disk. W ( 1 1 - i ) Pref ( - )2 i b friction in the shaft, and spring load if the check j 1f1 = 'd' ref Wref valve has a spring. (III is the pressure difference across puer t = tf + t, 4 tb + ts SP is the mass flow rate through penP 0 D s the fluid torque on the disk W is the power at full speed i where: i = AP A R Prof f is a bearing loss coefficient l fb sin ( *. e fh) is the torque des to is the pump efficiency tw= W RD eg weight of the disk q .2 IAhta is the torque due to friction Falves are included as flow arets which change as a N t "#'R %cg Der en shaft from centrifugel b function of time. The perameters in the annentum equation which are affected incluce the inertial lead on the disk f length and the flow loss coefficient. Reducing the area of a connector will increase the pressure drop is the friction coefficient en the shaft M across the connector and will cause the flew rate ts-Kg 3 sin ( de - 4 s) is the torque due to a threagh the connector te decrease. Imposing a change R in a flow area as a fumetton of time en a flow spring connector is strat htforward and is easily handled Ap is the area of the disk 4' directly in the so ution for the (fuld equations. is the moment are from the shaft to the similar to the imposition of a time dependent pump RO speed on the fluid solution as discessed previously. center of the disk F However, in the case of a check valve, dynamic equattens which determine the positten of the check W. is the benyant weight of disk assembly valve disk based on a force balance on the disk pust D r be added to the fluid solution in a menner similar te is the mass of the disk assembly 1 MD the solution required for the pump speed when the speed is affected by the fluid conditions. A typical Reg is the sement are from the shaft to the center of gravity of the disk asseadply l ' swing check valve geometry is shoue in figJre 2 and the equation of action for the disk is given below, is the angle at which disk hangs freely. [ 4 efh l t-(14) is the radius of the shaft l l q R$ = - 1-4 4 e ? s.

X, is th3 spring co:stant J s the tesquereture at node j T i R is the soment are from the shaft to the g spring Rg is the thermal resistance for connector k I e is the angle at which the disk contacts gt is t.be total heat flow in connector k s the spring AHk is the heat transfer area of connector k j {g rwuetian Hear Trander A conservation of heat flux approach is used to solve The integrated form of Equatten (16) becomes: for the transient temperature distribution in the i( metal parts of the geometry by dividing that geometry T.,,3-7, (21) M (Tr TjuRg - 5,Voi Into a nunper of control volumes and reesiring that PCYola + t n the not heating rate in each volume satisfy the at ,1 energy conservation eg'Jation. The not heat rate for on n a J each volume is written as a function cf the temperature at the centroid of that volisse and the where: Se is the heat generation per unit volume in resulting al etrait equations arr solved luglicitly. volume a The heat to uction equatten e n be written in the following form. Volg is the volume of control volme a T 18 the temperature in volume a at the s s (II) beginning of the time step 1 OC = V. J ,) g To ! ic the temperature in volume e at the nt I J..k 7T (II) and of tne time step where: J is the thennal heat flux There vlT1 he one equation like Eesation (21) for 5 is the heat source per unit volume each volume in the structure. The total set of k is the thermal conductivity equations can be represented by a single matrix T is the tesperature equation of the form: fe is the density B (22) C is the specific heat capacity A T = t is time where: A is the matrix of coefficients in Eq. (21) j i Equation (II) represents the condition that the rate T is the vector of unknown temperatures of change of temperature at a point depends on the B is the right hand side vector j rate of heat flow to that point and the rate of heat per. oration at that point. Equation (17)isthe Boundary conditlops must be imposed on Equation (22) definition of the heat flux, which is proportional to to represent the effects of boundary conditions on the temperature gradient and flows from higher the geumatry being analyzed. Three different types I temperature to lower tosperatura. The conductivity of beundary conditions are provided. These boundary is just the preportionality constant between heat conditions are treated as surface connectors which - flux and the temperature gradient. By substituting contribute to Equation (22) as additional heat flows Equation (17) into Equation (16) and assuming the as folloes. thermal ccaductivity is not dependent on position. l the norsel steady state heet condJction is obtained. 1. Temperature specified on boundary. The additional heat flom represents a resistance i 4T 2 path between the pode at the centroid of volume 5 (18) ra and the surface which is at a specified k7T PC - + = { 4t temperature. TB. Qk"AI(Im-II)/RIk (23) The numerical approach used to solve the heat t conduction equation is based on Equations (16) and i (17) directly rather than on the heat conduction where: A$g is the heat transfer area of the path equation given in Equation (18). By dividing the is the resistance between the node region of solution into a la e number of volumes R5k [ which are connected to each o her by heat flow paths tha valine centroid and the surface er connectors, the method integrates Equation (16) i over each volume and describes the heat flow in each 2. Heat flux specified on boundary. The additional canaector in terms of the Lamperature at the center heat flow is specified directly by the heat flux j of the connected volumes using the following on the beundary, JO. numerical approximation for Equation (11). Ok. A$ J3 (24) k Jk = l Tg. Tj) / Rk (19) 3. Heat transfer coefficient specified on boundary. Og - Allg Jk (20) The additional heat flew is represented by the resistance path between the center of volume a where: Jk is the heat flux in connector k between to the surface which is at temperature TB with a modes 1.j heat transfer coefficient, liTC. i l 5 3 E

m. -~ __ fluid solution. In the second cooperison, the f / 1"I,'$"% a g transiest heat conduction was calculated for a pipe suam smeen wall giren a specific heat tressfer coefficient and 3/!g8,;,,",,l"*l,* Lag,% an 1:ternal fltid toeperature. The second casa' tests the memorical approach used for the heat conducties 5e==== sa.- soluttee. we es+=dsw For the first case, the analytte solution predicts Nu asser r n'e"j the estabitshment of a were front at the end of the pipe which is suddenly pressurtzed and the wave front na se rs en propagates along the pipe at the speed of sound, on uneet ser ens no w reflecting from the closed and of the pipe at twice the incoming ampiitude. The poemetry seed Ia the om , ca s., n '* **'*a analysis and a descriptise of the reselts obtained ase a are provided la Figure 3. The results indicate that e e u the speed of proeagation of the wave front obtained ""'8"'"*' from the numerical technique agrees well with that f published in heference 2. The propagation velocity ~, of a pressure pulse obtained from the numerisal A k { soluties is only a function of the equations.of state 3 3 and the conservation equattens employed, and.is not g "- ,,,,,,, k;T g*L;*#,8 g* y espitettly provided to the solution techniese. m-e The poemetry and a comparison of the results a$btained for the heat conduction problem using the numerical o am, technieue to as analytic soluties are shown in Figure 4. In this case, the numerical technique provides accurate results for the temperaters distributten across the pipe 1 with as few as fear 8 weluees provided across the pi wall thickness, e r ciaew CtElpAR150M TO TURg11IE Trip l FIGURE 3 Test Problem for propagetien of a Pressure The approach outlined above was used to calculate the Ifare Treat in a Pipe transient pressure response for a turbine trip at a j l nuclear power plant. 'The turbine interceptor valves l used to isolate the turtise from steam flew are fast J acting valves which : lose in a fractica of a second Og - A5 (T, TB) / (1/HTC + RS ) (25) and can set up a rapid pressure increase in the k k i piping upstream of the valve. 4 The specified parts of Eeustion (11) are transferred Figure 5 shows a schematic of the system which was ts the 8 vector side of the equation and the unknown analyzed. The stesa generater, which supplies steam i temperatures are obtained by solving the resulting to the turbine, will react to the pressure waves which propagate through the pipe and the complete metris equation. steam generator was included to the model. The heat DESCRIPTION OF C0frUTER PROGRAM transfer u the steam generator aise affects the response and was included in the model. la the= l The analytic approach described above has been particular case analyzed here, pressure measurements incorporated into a computer progree to sinyllfy the in the pfplag were not available; however. the evaluation of pipe nation during transients. A absolute pressure in the steen generater and the considerable nusber of pre-and Post processing water level which is based on pressure differenfial i features have base developed to allow input data to asesurements across a part of the steam generator be entered eastly and to allow the results to be were recorded. The cosyseisen of calculated reselts interpreted quickly. The solution technique used has to measured results for the pressure in the stems i been optisited over the last several years to generator is shown in Figure 6 and indicates good increase the efficiency of the calculations to the agreement. The small pressure pulses recorded in the point where most transients which have been analyzed staae generator are a response to the larger pressure l l vill run within a few hours on an 191 PC computer or swings which occur in 3e piping between the steam 1 compatible. 5taple tramstents will run in a few generator and the intercepter volves. Calculated l cLinutes. pressure at ties interceptor valve is included in _ figure 6. ~ l CCBFAA!50f TO ANALTTIC RI5ULTS The recorded water level in the steam generator is I Results obtained using the approach outlined above shown in Figure 7. This measurenset actually were tempered to analytte solutions for two slaple esasures the difference in pressurg between two 2 geometries. The first af these was a sudden points in the steam generator and consecuently congressise in a pipe containing pressurized steam, reflects the pressure oscillati,ons prvduced in the similar to what might occer igstream of a suddenly piping. Also shown in the figure is the calculated 2 closed valve. This problem tests the propagation mass flow rate leaving the steam generater. The characteristics of the numerical approach for the sensured water lerel and the calculated mass flew 6 l l.

' ^ ~ ~, w let ] _ matrsia W.228 Pipe me11 20 timmem48 e . ee lege14ted . u tsea we&L f Ea,Se [ pese Tsametes onessamaans me I 8.2 ste/ses/ft / des F w&te See e. gees l Famid temperatuse i ' 4De setussam et i l 9 secumes 4' p. 9. aos = .P h 4 6 st ~ /~ seletten at ' ~ ~ ' i see l ggg. Enttia! coneAuse 1 2 Ceedoes&vitys.0033 954/seetsg fgeg r e..t ce, sty,.1: swswee, r e.n 1.s I g __ e.. se.satts 499 16s/f6 ..e e.n r,..us..: noe a w uv i F181mE 4 's9,, I Test Probles for Heat conduction Through a Pipe Wall l f t y b =t toe l 1 t F 7 t l $1'se.stees% f T_ sete as fee l M-W feet of min steam ) F ] N Lise 5 j Laus I + t r.d w I m _r 4 f ^ / I b g-seu r e 1 j l 'L,, r L~ h m ve yme e.s g 4 Y l I y nets f d K' C# I f_ I i I._ ,1l 1 i a T ..m i- - I.._ c 1 7 w i tas esli I ansessa.c 8'**=d"* 5H* t

  • e**'"

N FIGURE 5 Camputer Model for Turbine Trip primwr liet ) i 1 I 1 1 a

The resses rete respond at atest the same frequency. the steen gamerater flow resat:s high at the end of the transient is encaisse safety valves and turbine h.

s. n to..i 8 wl by 7 ass valves opened as a result of the transient.

saamma.-. [ j ! {'"' [ COMPAR150el TO PIPf, IWTION DATA Transient data for pipe motion at power plants is } "8 difficult to obtain since measurements are not normally avellable for severs treestents which cause 8*- s However, the magnitude of significant pipe metten. the mettee can sometimes be inferred free u.s consegeestial damage, such as deformation of piping n.sy sepports er from scratch marks on piping or terti insulatten. Several plant transients have been p g., y analyzed by the approach described above and results g nJ - l consistent with the observed damage have been pies. l/ se.:y obtained. Two such incidents whica have been 4 i m' 4 m 4 'n'

  1. dj analyzed are described below.

j J* Two recirculation pumps are aligned in parallel. j l. in order to allow the pumps to be operated "'ji [ individually, check valves are installed at the l ,, s t, discharge of each pisus to prevent the flow from a single running pump from passing titrough the .N ,.a When both pumps are running and secured pump. one of them is tripped, the check volve at the a.: discharge of the tripped mano will close and a 8 3 s a a e s a e se a u ves,. In the case natlysed, g3 waterhammer event occurs. l significant deformation of a pipe support near the suction side of the tripped pump occurred. FICURE E An analysis of the transient was used to Pressure Comparison for Tuttine Trip accurately predict the deformation of the hanger and to determine if the recesign of the htnger une was adequate. i as A disk in a control valve broke frwe its g,,,, attachment suoport end freely floated within the 2. f ' '" } 3" Tne design of the valve was such talve body. that the disk was unstable in this condition. I sn The interaction of the disk motion and the j i resulting pipe response set up a severe l vibratten transient in the piping system, 8" dameging several supports on the piping system. 1 ) An analysis of the transient was used to r,btain 8 4 piping loads which were consistent with the e-i 8',. d i observed damage and the resulting calculsud e se, stresses in the pipe were evaluated to i une demonstrate the integrity of the piping. l cainated n* 1' ' #w CONCLUSJDN isse. The analytic approach described above, and its laplementation in a couputer program which is easy to 4 use and runs on a personal computer, has proven to be , m -{ 't ~ a useful and practical tool in design work and in m ) evaluating power plant problems. .o j j j R(FERENCES f

1. Porsching. T. A., Murphy,4; a Fully Implicit J. H., Redfleid, J. A..

and Davis. V. C., " Flash. I Fertran IV Program for the Digital $leulation of t .in Transients in a Reactor plant March IHf. i e f i g WAPD-TM 840, Bettis Atomic Power taboratory. ta= 65. -*i FIGURE 7 Ceaparison of Steam Generator flow to

2. C. A. Meyer. R. 6. McClintock. G. J. Silvestri, Meawreft Water Level for Turbine Trip and R. C. Spenser. Jr., 'ASME $ team Tables. Fif th Edition' 8

3

I TRANSIENT TWO-PHASE recua,cu co r, BLOWDOWN PREDICTIONS OF AN INITIALLY STAGNANT SATURATED LIQUID STEAM IN A VESSEL USING TRAC-PF1 YASSIN A. HASSAN The Babmet a inicos Company, Nuclear Power Division P.O. Box 10933, Lynchburg, Wginia 24$06 0933 I

16. 1984 Received October Accepted for Publication January 14,1985 o

Mf5MENNsTrEIEES$fNTMMEEMOS { Comportsons of the predktlats of the best estimate pret-surized water reactor TRAC-PFI/ MODI computer code to ,L data of the General Electric levelswelltests wre performed. l esowsnm l Various Isme-step sites and nodalization schemes were em. j Ortf\\ce played. With appropriate time-step size voldfraction dis.tributlJRs pet voidficctions inferredfrom the measured data. Ncnphysi-6 col oscillations in spctlal void profiles were observed when i;; _~W a large time step was used. Comparisons of TRAC predic-4 tions with results obtained using three codes af the P.ELAP family wre performed. 'i"" d fMIMW*"*** WIM. hie 5EE$$EEEEEETI E ij (,Y"" o INTR 000CT10N y 9 Simulations of two small vessel blowdewn tests were per-formed using the best est.tmate pressurized water reac:or (PWR) TRAC.PF1 (Version ll.6) computer code.' The pri-rnary objective of these experiments, conducted at GeneralU 9 Electric Company (GE) (Refs. 2 and 3), was to investigate blowdown phenomena such as two-phse mixture level swell and to investiga.e void fraction distributions during blow-down. The two-phase blowdown phencroeson is a subject of - Suppressen great laterest to both che chemical and power industries. It. Pool is particularly pertinent to steam water boilers and to pres. surized and boiling water nuclear reactor systems.The GE swc!) blowdown facility co Fig.1. Schematic of GE levet swed test. pressure vessel, a blowdown line containing an orifice, and a suppression tank at atmospbetic conditions. A schematic tion as the vessel was blown down from its initial state, par-drawing of the test section is depicted in Fig.1. Detailed descriptions of the test are presected in Refs. 2 and 3. The tially filled w'.th saturated water at ~6.90 MPa (1000 p This study presests two s'unulations of two GE level tes pressure vessel was a 4.27-m- (14 ft)long and 0.3048-m<l.ft) usics the TRAC PFI/ MODI computer code. Compariso diam vertically oriented cylindrical tank. Instrumentation included six differential pressure (DP) cells spaced at equal between the TRAC-PFI predictions and the experime axial intervals in the vesset. The enessurements obtained from measurements are also presented. these DP cells were used to infer the void fraction distribu. VOL. 69 JUNE 1983 NUCI. EAR TECHNOLOGY 4 388 'y a-

m (l in.) la diameter. The saturated liquid level was 3.17 rn (10A ft) at 6.97 MPs (1011 psia). The seco 0.009523 simulation, a bottom break, was performed usfog the sam TRAC MSOtt DEgCRIPTION f orince size.This case was init all-f with 3.06 m l he TRAC-PFl/ MODI computer code was developed at i saturated liquid at 6.93 MPs (100$ psia l les Alamos National Laboratory to calculate the ther. mal-hydsauti i transient conditions. TRAC-PFl/ MODI solves the s x con.servation e break junctiott at time zero. i that govern tutive relationships to model the phenomena mass, momentum, and energy exchanse be-ween the phases. PRiDicT10Ns AND COMPARISSN WTTli SATA These relationships play a major role in the code predictJotts. The numerical solution scheme used to solve the conserva-Top Bloendown Test l d to tion equations for two-phase flow is carefully formu ate The top blowdown test was simulated using TRAC-avoid nonphysical oscilladons. The stability-enhancmg two-PFl/ MODI. The TRAC prediction ci the vessel pressure ~ step method used for one<ilmensional flow eliminates themateria f transient, obtained using the homoge break junction. is compared against the measured pressu Fluid system modeling using TRAC-PFI/ MODI is in Fig. 3. The TRAC predictions usla

nents, accomplished by constructing modules to describe the vari.

ous components in the system and configuring the compo-hb k tional cases. one with no additive loss coeffx:ic cent modules in a manner that best describes the system. and one with an additive loss coefficient of 1.0, are a Component models available in TRAC-PFI/ MODI include h presented in Fig. 3. As expected, TRAC underpre PIPE, TEE, $ TEAM GENERATOR, PUMP, BREAK, FILL, an transient pressure when break orifi ll t tem.The basic model used to simulate the GEicvel swe tes s uses a 14-cal! PIPE component to model the vessel, a loss coefficient of 1.0 was used. The transient void fracdon distn% don is strongly dep BREAK component to inodel the blowdown orifice, and adum dent on interfacial rnomentum exchange between and steam phases. With appropriate time-step size an ary conditions. This mode! is illustrated in Fig. 2. di d by Vessel top and bottom break locanons using various tial detail, transient void fraednn distribudons pre cte blowdown orifice sizes were considered in the GE level swell l i was tests, in this study, one blowdown test at each ocat on simulated using the TRAC-PFI code. Test No.1004.3, a topbrea

  • 7 Break Slas = 03525 mm 1000 -

Initiet Miscare Level = 3.17 m initial Pressure = 6A7 MPs g "I l Bresk Outiet - Dets j\\ --- *ssou,e m = 0 m 14 s= Pressa IK a f.0) 5 Pressure (K = 0,0) u s , 700 -{\\ k 4 u 7 000 @q-- = 4 1 n 10-N ~ e 500 9 3 \\ \\ g g 7 =2 } \\ 200-I \\ 4 N 100-3 j

  • -CellNumtwr 0

So 100 150 200 250 300 i e 2 Time (s) ( 3 Fig. 3. Comparison betwen the comptned an A Fill Component deprescrization of GE levet swu test 1004-3. (Mess Flow Rate a 0.0 kg/s) Numper Fis. 2. TRAC.PFI nodios for the GE smalt sessel blowdown. 389 VOL. 69 JtlNE 1985 NtJC1.EASL TECHNOLOGY ~

a w v-r rsius m v = uv a n r nu.u.-..... 4' rsassan Axial Distance (rni Axlel Distance (m) 1 2 3 4 1 2 3 4 e i a a a - i i t a 40 s 1.0 - gf . t er 10 s 1.0 i ~ l f a Data lll j - TR AC.PF1 (At = 0.3 s.14 Noce) 0.8 -

TRAC #F 1 (at e. 0.3 s,28 Nodel 0.8

~4-TR AC#F1 (At 85 0.1 s,14 Nede) l h -0 Data -*- TR AC.PF1 (At as 0.3 s.14 Nodel l l# A (A M s,28 N el ] [ OA ,f --e-TRACPF1 (at = 0.1 s.14 Noce) .f0.5 l 8 y f. \\ m I e 5 l 3 g Ol I u 04 - ) l D.4 1 4 JL,$ O 0.2 p / D 02 = ./ '''i''r''i 0 4 6 8 to 12 14 0 2 f' 0 4 6 8 10 12 14 0,2 Axial D: stance (ftl Axlal Distance (ft) Fig. 5. Comparison between the computed and measured vo Comparison between the computed and measured void fractions at transient time r-40 s for ses: 1004-3. flg.4. fractions at trar.sient time r = 10 s for test 1004 3. TRAC-PFI produced a smooth and accurate predicdon of TRAC-PFI compare favorably with the vold fraction diatd-the spadal void distribution, butions inferred from the mensured data. Predicted and men. sured void fracdon distribudens obtained at 10.40.100,and

  • Bottom Blewdows Test 160 s after rupture are oresented in Figs. 4 through 7, respec-tively. Nonphysical oscillations in the spatial void profiles T12e bottom blowdown test was simulated using TRAC-were observed whers a time step of 0.3 s was used. The ese!!-

PFI with homogeneous flow friction factors and additive loss lations were eliminated by decreasing the tirce step to 0.1 s. coefficients of 0.1 and 1.0 in the break junction. As shown An increase in the number of computatior:al cefts used in thein Fig. 8, with an addidve toss coefficient value of 0.1. vessel model from 14 to 28 did not clirninate the oscinadons. TRAC overpredicted the pressure in the transient period of It is suspected that these time-step related oscillations result20 through 30 s and underpredicted the pressure at transient from the explicit velocity dependence in the friction factor times >30 s. This discrepancy between predicted and men-function forms and the strong void fraction dependence insured results may be due to the lack of sufficient spadal the interfacial shear corralations, detail near the break to capture the exit void fraction. The The TRAC prediction of the void fraction distribution TRAC predictions of the tweshase level compare favorably at 100 s after rupture is compared with experimental results witt, the ineasured data, as shown in Fig. 9. and predictions obtained using RELAP4/ MOD 6 (Ref. 4), RELAP5/ MOD 1 (Ref. 5), and RELAP5/ MOD (Refs. 6 and 7) in Fig. 6.The RELAF4/ MOD 6 slip model produced CONCu!S10N1 nonphysical oscillations in the spatial void distribution that 1:verely ahered predicted void fractions in the downstream Predictions of two GE level swell tests were performed. cells. The RELAPS/ MOD 1 resuks were also osci!!atory, but The TRAC PFI/ MODI code results compared favorably with not nearly so severcly as those of its predecessor. The new the snessured data when appropriate dme' step and grfd sites interfacial drag model trnplemented in RELAP5/ MOD 2 were used. Nonphysical spatial oscillations in the void frac-improved the spatial void predictions significantly with 27tion distribution were observed when large time steps were axial cells in the vessel.' The codes RELAP5/ MOD 2 and Nuc12AR TECHNOLOOY VOL. 69 JUNE 1985 390

H:uan TWO-PHASE BLOWDowt* ruun.savna l Axial Distancs (ml li Axial Distance (mi I 1 2 3 4 1 2 3 4 a e a i 6 4 a i 1.0 - t a 100 s ID. t a 160 s i O Dau f} ' ( -+-- TR AC# F 1 l [ I . ~--RELAPSMOD2 lt g3 ~P-RELAP5/ MOO 1 OE - s ~6 -RELAPeeMC00 I U l Q &u f -*- TR AC PP I l s' (at W 0.3 s,14 Nodel [ l --- TRAC #F 1 - 0.6 j l 0.6 (at = 03 s. 28 Node) l ) b -e-TR AC-PP 1 E g' (At ou 0.1 s.14 Nodel fl 8 ~ , i '5 h I l / $~w' O.4 0.4

  • I jfb W

O g M 0.2 O.2 s / O 2 4 6 8 10 12 14 02'''''''''''10 4 6 8 12 14 0 0 Axial Olstance (ft) Comparison between the computed and measured void Fig. 6. Comparison between the computed void fractions usingvarious coda and fractions at transient time t = 160 s for test 1004 Fig. 7. i = 100 s for test 1006 3. . 7 s 6 ,N.%.%*N, 800 6 Experirnental Data o o - TR AC Calculation (K

  • 0.11 4,,

,600 -.- TRAC calculation (K - 1.0) g o ^ 3 400 o 2 1 w o 1 o f 200 O 40 30 0 10 0 Time (s) d Fig. 5. Compenson of TRAC prediction of venet pressure and experiment 391 VOL. 69 JUNE 1945 NUCLEAR TECHNOLOGY d

TWO-PHASE BLOWDOWN PREDICTIONS Hassan MRM 3,o 10

1. " TRAC Pf!/MODl: An Advanad Bat Estimate Ceewater 1

Program for Pressurized Water Rcactor Thamal.Hydraulie Anal-ysis." Los Alamos Nanonal Laboratory (;o be published). - 25 8

2. J. A. FINDLAY. "BWR Aefil!.Reflood Program Task 4.5-E 3:

24 ~} Modd Qua!irication Task Plat." NUREG/CR-1899. U.S. Nucisar s., s R..=m Com su-av.. i9sn. {6 s .e.o.a.,em. D,o

3. B. C. SLIFER and J. E. HENCH.
  • Loss of Coolam Accidems and Emergency Core Cooling Models for General Electric BoiEng e TR AC Calcutstion Y~L

. 1A g Water Reactors," NEDO-10329. Oscara! Elec.ric Company ( Apr. 4 g p 39733' g as

4. "RELAP4/ MOD 6: A Computer Program for Transient 2

Thermal-Hydraulic Ansinis of Nudear Reactors and Related Sys-tems," CDAP TR 003, Idaho Nadenal Engineering Laboratory 0 5 10 1ti 20 25 0 Uan.1978). Time (s)

5. V. H. RANSOM et d., "RELAP5/ MODI Code Marraal,"

Fig. 9. Compansen of predsted two-chne lswl sad experimen. NUREO/CR-1526. EGO.2070. U.S. Nudear Regulatory Comrnis-tal data for GE bottom vesse' : icadown. sion (Nov.1980). 6 V. H. RANSOM st al.. RE!.AP5/ MOD 2 Code Manual." ECC.SAAM4377 EG&O idaho. Inc. (Apr.1984). employed. These oscillations were not in evidence when a

7. H. CHOW and V. H. RANSOM. "A Simple Interphase Drag reduced time-step size was itsed. Reducdon of the spatial gnd Model for Nitmerical Two-Fluid Modeling of Two-Phase flow aire altered the character of the osdllations but did not clim-Systems." Trans. Am. Nascl. Soc.. 46, 853 (1984).

inste thern. 1 l l NUCLEAR TECHNOLOGY VOL. 69 JUNE 1981 392

i Report on Use of Full-Scale UITF Data to Evaluate Scaling of Downcomer and Hot Leg Two Phase Flow Phenomena l I l l l ( l l l l l 1 l l _m

i 4 I USE OF FULL-SCALE UPTF DMA TO EVALUAili 3EA.Imi 0F NWNCOIER (ECC sTPASS) AIS

un LEs Two-rtA5E Flow PMt.mmenA i

P. S. Damerell N. E. Ehrich a K. A. Wolfe i { MPR Associates, Inc. i ) Abstract ) The first UPTF Downconter Separate Effects Test and the UPTF Hot Leg' Separate Effects Test provide full-scale data useful for evaluating scaling effects. The downcomer test showed that subcooled ECC penetration down the downcomer at one steam flow was greater than would br. predicted from several j correlations using the largest available subscale data l (1/5 scale by length). This is a favorable result fra a j licensing standpoint, i.e., actual full-scale performance is i j better than thought. The multidimensional flow in a large downcomer appears to be a key factor in the better delivery at large scale. The het leg test showed that saturated water 4 ] runback to the vessel in a hot leg under CCFL conditions is very close (25%) to that predicted from the largest subscale i tests (1/13 scale by area). This is an encouraging result from the standpoint, of scaling. Further, this test shows there is a large margin between typical small break LOCA reflux i e condensation conditions and CCFL, and that the major scaled small break LOCA scaled integral facilities (PKL, Semiscale, i ROSA-IV, FLECHT-SEASET) operated within the hot leg CCFL i boundary, even though not necessarily at ideally scaled PWR ii conditions. Finally, evaluatien of these data show that runback of de-entrained water in a hot leg during large break i LOCA reflood is likely to occur in typical US PWRs, and the i data successfully explain the observation of runback in SCTF (full-height oval hot leg) and the lack of runback in CCTF (scaled height hot leg). ' Introduction Research on the effectiveness of the emergency core cooling system (ECCS) in a pressurized water reactor (PWR) has involved a large number of separate effects and integral

tests, essentially all at scaled geometry.

The large number of tests have provided useful data for models i and correlations of various pheonemena, and for assessment of integrated i 143

I computer codes for loss-of-coolant accident (LOCA) evaluation. One of. { the residual issues with regard to the accuracy of nuclear power plant calculations is the uncertainty introduced by calculating at full-scale i while testing and assessing at subscale. i l One of the major effects of scale is the impact of flow channel size on flow patterns and flow regimes in two-phase flow. Particularly during l portions of a LOCA in which velocities are lower and gravitational forces play a much stronger role, it is known that the size of the flow section has a significant-effect on the flow pattern, on the transport and retention of water in key areas, and thus on the occall course of a i transient. The latter portion of a large break LOCA and a maall break LOCA are examples of scenarios where gravitational (and hence size) effects are important. Recently, separate effects tests in the Upper Plenum Test Facility (UPTF) have provided the first full-scale data on two key two-phase flow i l scenarios in PWR LOCA evaluation. These UPTF data provide a unique ~ opportunity to evaluate the effect of scaling up to full-scale and to assess the scale-up capability of analytical and anpirical models. Al so, evaluation of these data provide improved. insight and assurance about expected PWR behavior. Accordingly, it is appropriate to evaluate the j data from these tests in this regard and the purpose of this paper is to describe the results of initial scaling evaluations from these tests. i The two UPTF tests discussed herein and the overall reactor safety scenarios to which they relate are as follows: i 1. Downcomer Separate Effects Test - This UPTF test investigated ECC delivery /Dypass in the downconer of a PWR. It is related to the reactor safety question of how soon and how quickly the vessel j refills with ECC water at the end of the blowdown phase in a large l break LOCA. The key phenomenon is the countercurrent flow l limitation (CCFL) in the downcomer (i.e., downflowing water in the i l face of an upflowing steam / water mixture) which is strongly affected by condensation and by the multidimensionality of the downcomer. This scenario has long been considered to be scale-dependent. US licensing rules '(10 CFR 50 Appendix K) artificially require no ECC l delivery down the downcomer until blowdown is concluded. Scale test results from the NRC ECC Bypass Program (up to 1/5 scale by length) showed ECC does penetrate, and empirical correlations to quantify 1 penetration were developed in that program. These correlations were generally thought to be conservative if applied to a full-scale 4 i P6R. Accordingly, this UPTF test (which was the first of four j downcomer separate effects tests) helps to accurately quantify full- ] scale behavior. i 14

9 s ,r I This UPTF test investigated 2. Hot Leg Separate Effects Test flows in the hot leg of a PWR. It is steam / water countercurrent [ related to the reactor safety question of how readily the drain-back of water occurs in the hot legs during a small break 1.0CA i (e.g., during reflux condensation cooling) and also to how readily i de-entrained water might drain back during the reflood portion of a-l This issue has been previously addressed with i Accordingly, the large break LOCA. separate effects tests up to 1/13-scale (area). UPTF data provide the first full-scale glimpse at this phenomenon. This report presents brief overviews'of UPTF and of the two tests (all of which have been presented elsewhere) and discusses the scaling evaluation I of downcomer and hot leg phenomena. j Summary Descriotion of UPTF and 2) and is UPTF has been previously described (References 1 l briefly discussed here with emphasis on the downcomer and hot legs. The which is similar to a US. 4-Ioop UPTF simulates a 4-loop German Pieta full-size reactor vessel and piping (four Westinghouse PWR (Figure 1). ECC can be injected hot legs and four cold legs) are included in UPTF, l One in the hot and/or cold legs of all four loops, or in the downcon 4 The four steam generators are simulated by l of the containment simulator tank. steam / water separators and the four reactor coolant pumps are The reactor, vessel four simulated by four passive, adjustable resistances. The core upper plenum internals and top-of-core are full-scale replicas. j l 3.Osummee vased tw Not tse @ hussessand. 1 I 1hnv esi f l I temsase.emshuuhw 3d Dio. eve Womed I. caid Las @ scc.humem masse g, sed tag 98'8 W 4 huipsm @ N""** 06"I'd Isses.Gammesw w See atediaplanAsg i l 56aankumme gc Isy gcm.modownesennene. assea y, g,g g, i. j f 5-g2 g'**='*2 g .m.s g m w i. Y en e m4 , to Qep> p 4_ ~ r e1 ( 6% o l j Q \\ 1 OVERALL VIEW OF UPTF (FROM REFERii!NCE 4 PIGURE 1 145 d

i -r ~ is simulated by a steam / water injection system with 193 nozzles, one for UPTF was each active fuel assen61y which would be present in a PWR. originally designed as an integral system test facility covering the end-of-blowdown, refill and reflood phases of a large break LOCA; as discussed in this paper it has also proven very useful as a full-scale effects facility covering both large and small break LOCA l UPTF can operate at up to 18 bar (260 psia) pressure and separate phenomena. 220*C (428'F) temperature. The UPTF vessel downcomer (Figure 2) has an inner diameter of 4.370 m (14.3 ft) and en outer diameter of 4.870 m (16.0 ft), giving 250 m (9.8 in). The four downcomer skirt to the cold leg centerline is 6.64 m (21.8 ft). 750 nm (29.5 in) cold leg nozzles are spaced around. the downcomer as The lower plenum is 2.48 m (8.14 ft) high from vessel shown in Figure 2. bottom dead-centgr to tht; lower edge of the downcomer skirt and i volume of 24.9 m (880 ft ). 3 Westinghouse PMt due to the presence of core simulator piping in the U f lower plenum. Table 1 compares UPTF downcomer anc lower plenum configuration with that of typical Westinghouse and Combustion ) Engineering (CE) US PWRs*. because these Babcock & Wilcox (B&W) PWRs are not discussed hereist Future UPTF tests are relevant mainly to Westinghouse and CE PWRs. UPTF tests will cover conditions relevant to B&W PWRs. i M -'gllf=' i N l 1 L -- s- ~ /\\ / 4, / 4 4 / d it Ep. -] 'r p' [! H -h ii. %; T s f I C J' l~ r j T 1 ill7.-. s e e-4MW- :s-

4
Ml:::r.,

OAft::i.inI_ "i,_ _ xj

== ~~ 7 g ',+-x.lf.g g W 5f

(

s l i N#a s L ---a= \\ __f_i g , i g, l{,/ l I q j 1 f I my

L fp2-o t...ni.n o.t.

1 1i.- si ke f ms+e g 3 ,c.e.e., a UPTF PRIMARY VESSEL (FROM REFERENCE 2) i FIGURE 2 146 _ _ _ _ _ _ _ __ _ ___________________ _ ____ _ ________________________________j

.m m.. - TAM.E 1 AttSON F UPTF famefuER Alm Gourm==uon unn urtCAL i' emen as w-emus m- -sum u;al PIA'S tESTh t l F7F Westinehouse CE Ptst volum Pts value Value Paremeter l 4.87 4.39 4.83 (15.0) (1464) (15.2) l Dounconer CD e (ft) i Deescener Sep 258 280 2s4 (9.8) (10.2) (10.0) as(in) 1' 4.64 5.33 6.46 5ttrt to cold Le9 Center s (ft) (21.8) (17.51 (11.2) D - amer Neight. 24.9 29.7 21.5 ty(ft )glenus volume (800) (1089) (794) a ( d has a -Each UPTF hot leg (Figure 3) is 750 me (29.5 in) inner dia J A 50' riser section rises 0.91 m (3.0 ft) at the end about 8 m (26 ft). of the hot leg attached to the steam generator simulator. In the i horizontal section of hot leg, an internal ECC in.iection pipe ("Hutze") j There was no is located along the bottom edge of the pipe (Figure 4). injection through the Hutre in the tests discussed in this report, l The Hutze blocks an area of i.e., it is a dead space in the hot leg. A Hutze 2 (0.478 ft ), about 10 percent of the total pipe area. Table 2 compares UPTF 2 O.0444 m is present in German PWRs but not in US PWRs. leg configuration with that of typical Westinghouse and CE US PWRs. D TABLE 2 COMPARISON OF UPTF MOT LEE CONFIERArt0N WITN TrptCAL utU tm-- Am weu6 son tastatusus tu; rour s 1 i 1 WPW Westinghouse CE Past Value PtR Vales value 1 P;.__;er / Diameter. m (in) 0.790(29.$) 0.737(29) 1.07(48) 1 %dreut te Diameter. e (in) 0.639(!$.2) 0.737 (29) 1.07(4Z) I Flow Area, m2 ggg!) 0.397 (4.25)* 0.427 (4.59) 0.894(9.62) ] 2 0.441s n! within diesster eines 0.0444 m blected by muta. i

2.7a c' 1.25 0 1.2s % 1.85 e _ (12.4 ft) (4.10 ft) (4.20ft) steen g' (s.esft)~ ~ generator Steulator 0.65 m

l

+/ l (2.13 ft) i I l I l D.91 m (3.00 ft) 1 so a = i i 9 i_ .m. I I / (25.5th). \\ ' 4 I i 5 l list Lag -c Locatten of samme Domsttemeter seems Vessel i j ECC Injeccles Nea21e j Core terrol j Dese einenstens are for the yw broken isop het leg, which mes the only het la the intact leeps, these

  • tests:

j leg used in the Het Log Separate Effects Test. tue dissestems are stigntly larger (3 86 m and 1.34 m). i ?i UPTF HOT LEG,CONFIGURA110N ^ FIGURE 3 i .'s.enum se.e n8 a

=. =

r es.nriw = =. e.n w te.no n 3 l geman p nar = s.mo e is.m as I ^^' i fA } l l W tA ,. g,, ] L,,,,*, % mi = I e i mean e n 6. so.= => l-lu al 1 "n, i j 1 '~ L...., .ui i esenow A-A CONFG1 RATION OF INTERNAL ECC IPUECTICM PPE (MUTZE) N UPTF HOT t.EG PImmE 4 148 i

-i' } Overview of UPTF Downcomer Separate Effects Test The test conditions and results from the first UPTF Downcomer Separate Effects test are described elsewhere (Reference 3) and are briefly reviewed here. The test was run in two phases: transient and steady. In both phases the loops were blocked at the pump simuistors, and the cold l leg break valve was used to allow flow to discharge from the system. i Also in both phases 30*C (86*F) ECC was injected into the three intact e cold legs at a rate of 500 kg/sec/ loop (1100lb/sec/ loop). A small amount of nitrogen (about 0.15 kg/sec/ loop or 0.33 lb/sec/ loop) was i injected with the ECC to simulate the nitrogen coming out of solution in a PlR accumulator. 4 In the transient phase, the facility was initialized at 18 bar (260 psia) i with the cold leg break valve closed and the containment at 2.5 bar (37 psia). The lower plenum was approximately half full of saturated l water. The test was initiated by starting ECC floit to the cold legs and i opening the break valve to full-open at about the same time. This i produced a depressurization transient with stems (from expansion and flashing) and entrained water escaping up the downcomer and out the i l break, and subcooled ECC water entering the top of the downcomer from the three intact legs (Figure 5). The transient lasted about 25 seconds. e B troken /, 'I*""' / Cind W l Cold Lee V, l i f l ^ r 1 o ,,, s N sec l / \\

    • I******

stees riew / s / j se=a core o Nve,< ,3 Nf, ] l\\ to aresam eeeeeeeerisessen / j j t l I / / c,,, / f t i r i i h I j t j ( i ---. et.o. ri / 1 =a e., ri, i i ~~e per stay 11ettr. ) met t.=,s we.c =%.a rtasune/ensre tee,ess Due to Depressurtsetion OlAWWWA OF Pt.OW CONDITIONS DUfWNS TRANNENT PHASE OF UFTP DOWNCOMER SEPARATE WPECTS TSST PMUIE 5 149 u---

l i In the steady phase, the facility and containment were initialized at There was a 2.5 bar (37 psia) with the cold leg break valve fully open. j To start small initial. saturated water inventory in the lower plenum flowed to the lower plenum, up the was injected in the core whichAfter a few seconds, ECC injection in the j downconer and out the break. The downcomer test was over in about cold legs was initiated (Figure 6).20 seconds at which time the low the core. 4 As discussed in Reference 3, the transient phase showed a mixture of ECC t (out the break) and delivery down the downcomer. At the conclusion of the blowdown the lower plenum was nearly full, i.e., the bypass Local downcomer measurements inventory increased during the transient. i showed a strong asyneetry in the flow, with ECC delivery preferentially i The steady occuring on the side of the downcomer away from the break. phase showed nearly comp.lete penetration (about 80 percent) of ECC down l the downcomer against the upward steam flow. Once again, local downcomer showed strongly asymetric flow with ECC penetration measurements favoring the side of the downcomer away from the break. 4 ) EM - l / seek" / cetd Les

    • $b t

+ } spyer l 1, *= % % Plenius ~r \\ / b / / not j / %g zasweien ] / Y j l } \\ m ^ d It iI 1 d~' ..e ,1 i and Up j j f f+' / / I t-1 1 s) 4 v i i ,,.e ---o unter risw nt., 4 j por stapitetty, seems rien in Cese finittater I Injeetten Pipes I ORAMAM OF FLOW CONDITIONS OURN3 PSEUDO--STEADY PHASE OF UPTP DOWNCORAWI SMRATE EPPEC13 TSBT l MOURE8 l 150

t i i Evaluation of ECC Delivery /Syoass Scaling To best quantify the results of the UPTF downtoner separate effects test i for evaluation of scaling, mass balances were perfomed for each test The results of the mass balance are shown in Figure 7 for the phase. transient phase and in Figure 8 for the steady phase. Figure 7 snows that when the transient started there was a period during i This storage was inferred which ECC was stored in the intact cold legs. frns thermocouple rakes in one cold leg which showed subcooling appearing There were no direct measurements at all locations over this time frame. of mass stored; the curve shown assumes the closed and I of the amount Vessel inventory decreased pipes filled according to the injection rate. slightly while the legs were filling due to flashing. i When the cold legs filled and water was being delivered to the downcomer. vessel invertory rapidly increased, indicating ECC delivery. Small indications of bypass out the broken cold leg first appeared at this time l Over a period of about 15 seconds, delivery and bypass both as well. The " spike" in delivery is apparently attributable to a brief occurred. septying of the cold leg inventory -- a corresponding de i

measured, as discussed above.

At the end of the i rather than i (about 25 seconds), the lower plenum was essentially depressurization full and less than half the injected water had been bypassed out the i l broken cold leg. ( tol ICel, l i e.== r "4 "t.PM:;'{try,' kl

=

0 8 _..f.uwu.=.w.u ) L___. / r ~, aY / '~ - ,,e = trute. (s' d tog Fles y i 7 ,7 i u a es a o 1ese efter Start of NC IWasst.e (ses) [} LFTF DoWNCoMeR SEPARATE sFFECTs Te8T MASS eAL.ANoe FoR TRANelENT PMAse neure 1 151 ~ r--.-

l ,r Figure 8 shows that during the steady test there was also period during which the cold legs filled, followed by. substantial ld leg. At delivery to the vessel with limited bypass out the broken coof ECC in approximately. 20 seconds after the startand only 20 percent of the ECC had b plenum was essentially full, bypassed out the broken cold leg. The evaluation of scaling using the UPTF te they are Figure 9 shows a downcomer dimension discussed - first below. plot using the parameters j

  • and jf* where g

g ((p f. p ) g )1/2 y bg)1/2 7p g M g j* = g g f (P f)1/2 4 { g ((pf _ p ) g )1/2 g g M j f* = M = mass flow rate of gas or liquid where 2 forUPTF) 2 or 39 ft A = downconer area (3.62 m p = density of gas or liquid f g = gravity W = downcomer circumference (14.5 m or 47 i 1 /

=

M,les ( l..t ... ~ i ("',',F:"lll!.'!".'. + y i'~~ihn k.f.r / [ f u.} f ic7 w. he oms em / j ~ tten after geseg of E tedertie (ser! UPw oowwooman surAnm arrects raer l uAss nauwas con ersAoy Pnass PleunE 8 152

a (j * - F j,* Tcond)1/2 + g jf 1/2, j, Correlation 1: g g i ~ urn ASSOCETES 1/2 + gjf el/2 = C p.rs-as-isce Correlation 2: j *1/2. y j g j stastsy i, i d

  • Tcond " de in I*

) d*" g, f g Musente Flux Scaling J

  • Scaling J

Parnanter Correlation 1 Correlation 2 Correlation 1 Correlation 2 f F 0.281 0.209 0.281 O.209 4 ) M 0.896 0.822 0.896 0.822 C 0.250 0.230 0.369 0.344 i I 0.20 w 4 I i i \\ ~ UPTF Result g \\ 0.15 - \\ UPTF CCFL Prediction Based \\ l on Two Correlations from l 5 \\ scaled Tests J* Scalinc) j UPTF CCFL Prediction Based Ns 1 j l - g on Two Correlations from-l 5 0.10-scaled Tests (Momentum Flux [N 2 4 g % ' Scaling) g/ l C s%

  • % ' % L,'

g i e

    • =.

3 1 l 'A f f 0.06 N-2 i 5 i l E i Es 0.02 0.04 0.06 0.08 l g O Dimensionless Liquid Flow Penetrating Down the Downconer, j,

  • COMPARISON OF UPTF DOWNCOMER TEST RESULT 1

WITH PREDICTIONS BASED ON 1/5 SCALE TESTS FIGURE 9 153

f ,r From previous scaled tests in the NRC ECC Bypass Program (Referen J 8), j* correlations were developed using data'fromA convenient sumar j J 1/5 scale (by. length). J Reference 4. l The curves shown on Figure g represent the CCFL boundary calculate UPTF based on the largest scale data available from th l tests (1/5-scale). the two lower curves represent a " constant calculating the UPTF boundary: momentum flux" scaling approach with two different forms of correlating the 1/5-scale data; and the two upper curves represent a " constant j' scaling approach with two different forms of correlat I correlated some of the subscale data more favorably -- there is no clear data. i The lower curves are the NRC-basis for reconnending one over the other. recomended approach for downcomer CCFL based on the scaled tests i The upper curves represented a more " realistic" approach which was not reconnended by the RC because it could n NAC ECC Bypass Program. i to be conservative, at full-scale based on the scaled The main result of the UPTF downcomer separate effects test is demonstrated i that the full-scale test shows more ECC penetration than would be l tests. predicted by either the NRC-recommended or realistic approach j Hence, there appears to be a beneficial effect of large scale. to improved condensation, to large channel l scale. which may be related The observation of the strong asymmetry in the hydraulics, or to both.i.e., preferential ECC downflow on the side away from l break (see Reference 3), indicates that the large channel effect is downcomer, probably significant. The min result of the transient phase of t'he dow i i even while the primary system is continuing to Although scaled tests suggested this would occur, this Iower plenum i The UPTF test was depressurize. full-scale test provides the best direct evidence.with regard to lower reasonably PWR-typical subcooling. The ECC injection rate was somewhat low and the l depressurization somewhat prolonged in comparison to a typical PW l but these differences do not affect the validity of the o l j discussed above. benchmark analysis case for computer codes. It is not feasible to run in UPTF a direct counterpart transient test to i previous scaled ECC bypass tests, due to some particular choices made in plenum volume and containment pressure in the previous sca facilities. Accordingly, futura downcomer separate j PWR-typical) led effects tests will focus on steady-state downcomer CCFL conditions, in an 4 attempt to further evaluate scaling by comparing UPTF results with CC curves derived from previous scaled tests. 154

l i i j . Overview of the Hot Leg Separate Effects Test j The test conditions and results from the UPTF Hot Leg Separate Effects Test are described elsewhere (Reference 9) and are bri efly reviewed here. The test was run using only the broken loop hot leg of the UPTF. l The test was performed as several ste.My phases, each consisting of staan injection into the primary vessel unwh flowed out the broken loop hot l 1eg, and saturated water injection in the steam generator simulator i plenum which could either flow back dawn the het leg toward the vessel or i out of the systes through the steam generator simulator (Figure 10). Six ~ separate steady flows were obtained at 3 bar (44 psia) system pressure and 10 flows were obtained at 15 bar (218 psia) systaru pressure. In all cases water flow was established prior to steam flow. The intent of i obtaining several flows at each pressure was to " map out" the CCFL boundary. Also, one of the flows at 15 bar. simulated conditions in a i Westinghouse 4-loop PWR during the reflux condensation mode, which can l occur during an SBLOCA. i i d l Seston A.A SeadenB4 I h Ans -emas mi s, n.m 4 oom sur een= 43fM ml Nem \\ l +__. ( Q 1 % C 7 =" 1 Nm - -s $tsamhuster I asseman 'g,W: > 1, i sL 4 l % = esth6sessa M i A-i hostpuum 8h'" 11 / amme ning i tem 4 s % sgehu M * LY L n 2.secess/ ) le 8"Ima i=P 1 esse aseuseg a luthe J i ) i UPTF HOT LES SEPARATE EFFECTS TEST i OVERALL PLOW CONOmONS wnohi nsPERENCE 41 f FIGURE 10 i n i 155

= -. e i.. w in a w nm c 5.- i I.i %7.2 i 8 a 1 s i, ?,.$**d5-*Y E ~ n, l . /f"* sb. n, 4 _n:.m r. I't 4.,vsa m. Hm.

s. er -

urir war tea sepAnAn erween nur SuheedARf 0F DATA RGURE 11 shows the measured flows at the two test pressures, and Figure 11 Figure 12 shows the data on a dimensionless j* plot, where g(P)1/2 /p A (p f -p g)gD) M h j* a g 9 g t Mr(O)1/2 /of A (@ f -p g) gDh jf* = f is the hydraulic diameter. The variables are as defined previously and Dh which is.639 m (2.10 ft) for the UPTF het leg at the "Hutze". r 4 6 ::Y.'::".M/ l 1 ,7-i - %'."l"; 5:'" .: u. . a.. ir-'* }u-p. g- .3-w,,,

s' g-o 77

.J. .t i ~ .m ..ss s.ts s em .g WPT, H0f LOS 99.pemAN BPPECT5 TEST anguLTS s.0usW OseJ' PLAT PegamE W W

i -E 1 On _ the j* plot, the 3 bar (44 psia) and 15 bar (218 psf a) data correlate t favorably. The line drawn through the data on Figure 12 is the "best-l fit" experimental correlation to the UPTF data. l i The -results of this test provided direct demonstration that there is significant margin against hot leg CCFL during the reflux condensation phase of an $8LOCA. This is shown in Figure 12 by the fact that the i " typical" point is substantially below the CCFL boundary. This point was chosen based on conservative assumptions such as relatively high power and one steam generator inactive, etc. Accordingly, this result provides q direct and convincing evidence that substantial margin exists. j Figure 13 shows the measured hot leg level and void fraction for all of i the tests, plotted against j

  • the dimensionless gas. flow.

Thes'e data i are from a three-beam gassaa 8en,sitorneter located just on the vessel side i of the hot leg riser bend, as shown on the figure. There is no "Hutze" obstructing the bottom of the hot. leg in this short section of hot leg. l The data clearly indicated a stratified regism and show significant water presence in this region of the hot leg. These data appear to show that CCFL is being controlled by the hot leg (i.e., CCFL is not occurring in the riser or steam generator simulator), since water is not absent from l the hot' leg when there is zero net penet' ration to the vessel. pZ .04 lJ.*rrC.1;h i m - p _ i w._ LAs t ' \\. - m.i::-- g( ,\\ us-l A, r.,r - = ="a-rw er 4 menan I a. "e

u-J gw I

I i m. y g,,.

y 8

d he$ e 4" "~ .. j' LFTF Hof leo SEPAllATE EFPECTs TEST DAEAgustED Mof LEO LEVEL AND VOC PflACTION AS l A FuMCTION oF oWENSIONLK85 STEAM VELotNY l u. I 157

i fI Evaluation of Hot Leg CCFL ' Scaling f J I Several theoretical and scaled, separate effects studies of hot leg CCFL l or generalized horizontal channel CCFL have been carried out, including: L Richter, et al (Reference 10) - 1/13 scale by area compared to Westinghouse PM l Gardner (Reference 11) -- Theoretical .0254 m (1-inch) square channel i i ~ Wallis (Reference 12) (approx.1/660 scale by area compared to Westinghouse PWR) i ohnuki (Reference 13) -- 1/840 scale to 1/93 scale by area compared to Westinghouse PW i 1/210 scale by area compared to Krolewski (Reference 14) l Idestinghouse PE i Also. Transient Reactor Analysis Code (TRAC) predictions of the UPTF test l were perfonned. Each of these previous studies provides a way to predict full-scale hot leg CCFL behavior. In all cases, j* is the key parameter in scaling. 1 shows the UPTF data compared to the full-scale predictions Figure 14 based on five of the six studies mentioned above, on a j* plot. In the i \\N (Mn \\, l Q-ax /=--, i yN'n2 = 4 i pv useem=> j

== l x&% o T o ne m. o. o. a ww n.swa=== T r OERdran00N OP DaBL TO TIEENIETIGhL tegenLB Age COINIE.Anoud8 FRome meALL SGALE TasTB FlulNW to 158

t g [." im%a U*E7d=% ' [/ dg 1 M."-r-j / i 4 s. w s,*. m.7 toimee f,,',,",,,", w" "'"" 8 N er N (a.r.c:::. Q. 3 n. m, we -..aue . v. u. , gew I u. leur e. : e we.. i s.e. .. en -,y.,, s.3 L u. I 4 a s j sammensais-e--nc.: se. n,. s,. u UPTP HOT LEG SEPARATE EFFECTS TEST i COMPARtSON OF UPTF HOT LEG VOC PRACTMS TO 3 WALLS CORMELATM rnURE ils i case of the Wallis correlation, which is a [*/ void fraction correlation, i the comparison is on Figure 15. The results of the comparisons shown on Figures 14 and 15 are as follows: Very close ag/eement is obtained between the UPTF data and the i Richter, et al correlation, which is the largest subscale data i previously available. The agreement is 15 percent. This agreement confirms that the j* correlation approach appears to be valid. The close comparison indicates that scaling up across an order of magnitude (ba. sed on pipe area) is successful and is therefore. an i encouraging result. Closa agreement is obtained between the UPTF data and the Wallis correlation which is based on void fraction rather than liquid I flow. This indicates that the basic approach of this correlation (once again, a j* correlation) appears correct for scaling, but that implementing this model to calculate liquid flows is dependent on knowing an accurate void fraction. 4 i 4 159 d

Significant deviation is observed in the case of the - Ohnukt Krolewski correlations. and This is considered to be due to the sea 11 scale of the underlying tests and the strong effect of the riser bend in the previous tests. angle) could significantly affect the flooding.t l .., length and i this sensitivit It is not known if up" these smally is PW-typical; this makes it difficult to " scale-scale results. I favorably with the UPTF data.The predictions using the Ga the model (f.e., unstable stationary disturbance) does no i realistically reflect the true flow behavior in a PW hot leg. r to 1 i The predictions from TRAC show a nearly "bi-stable" behavio changing gas flow rather than the l reasons are still being investigated. gradual CCFL boundary. The [ Overall, the comparison with previous theoretical and scaled res very favorable in that the results from simulated hot leg separate s-accurstely predict full-scale behavior. effects tests with one o I i In addition to these separate effects comparisons discussed abo several Plat integral tests of small { conducted. In the small break case, these faci' ities demonstrated refluxand larije condensation occurs without apparent hold-up due to hot leg CCFL. i, major small break facilities investigating reflux' condensation are: The Semiscale (References 15 and 16) - 1/1705 scale FLEcliT-SEASET (Reference 17) -- 1/307 scale s L PKL (References 18 and ig) -- 1/134 scale 1 ROSA-IY LSTF (Reference 20) -- 1/48 scale The conditions achieved in reflux condensation tests SBLOCA facilities are plotted on a j* graph along with the correla 1 cale UPTF results in Figure 16. i Also shown in this figure is a band of "PE of conditions" which roughly i envelope SBLOCA reflux condensation conditions. This figure shows that although the scaled facility the CCFL boundary, conditions tend to be scattered about the gr i as are the PWR conditions. The PKL points, which deviate most froe PW conditions, tend to be a result of the hot l scaling used in these tests, which did not seek to preserve j* a i eg area other tests. The major conclusions, though, are that for all of the I 4 + I 1 4 i i 160 3

l l l 9.# - yhes., s 1- } {b== .au,..m j 3 j y A DEA-IV4.Str S.8 i .:;L.. 1, 't._ ..,,$g;;r cowasou or meAu.-sens racun i fisFLAN CONDetEAfl006 EXPEIWMENTAL CONDITIOett 10 uPW TEST RESULTE PeguftE te i i facilities. the observation of reflux condensation without hold u het leg CCFL is consistent with the UPTF data, and that the sc rom facilities did not distort PWR hot leg behavior in a major phenomenological way. The reflux condensation results are applied to US PWR's on F This Hgure shows hot leg CCFL curves calculated for the m e 17. Westinghouse and CE plants (3800MWt) in both cases) at 80 bar (1160 psia). are conserva(tively calculated Also shown condensation both cases.. conditions for both plants. The large margin is evident in SBLOCA reflux In the large break case, hot leg CCFL is only an important cons during the reflood phase of the transient., The major, large scale reflood facilities which allow a detailed evaluat%n of hot leg eff on are: Cylindrical Core Test Facility (CCTF) - 1/21 scale i Slab Core Test Facility (SCTF) -- 1/21 scale with full-height ho leg 161

.35 .H- .o- .r .n - i,s =_ an. n ,=4 .n. =

i..=i 6...

= g g...,.g =. -*y lg j 2 I*I s i [J. -D=- -n T3 i =- n. -.i l t g

!,3::M

= s J,,,_ =.. <.L. i A l j ' 1... j c ..e g3 lli'aSU" ir*="'nalL ~' i j ___C.ne,tt.as %._ Canditi.e.h j* 'gg., 1 _(_.__ =- fin!#uf"FJ :J'J" 4 i

    • '4:#::* 4!!ia": W.M::,,

ai - l 1 s 4 's s 4 s s mass n nae. er Cem mne u.ser, l Ar (kg/s) la One N.t Lag ). i l PnEDICTED HOT LEG GCPL BEHAVIOM IN U.S. PWRs { 1 COMPARED WITH 85LOCA REPLUX CONDENSATION { PLOW CONDmONS i Pieuna w l-l In CCTF, no evidence of counterflowing water during reflood was observed. i [ 1.e., any water reaching the hot legs tended to be swept through the l-prieary coolant loops by the steam flow. In SCTF, though, hot leg water i runback to the vessel by countercurrent flow was observed and directly ] measured. It is noted that due to the unique cross-section of the SCTF l i hot leg -(oval) there may have been greater de-entraineent and more water l available for runback in the hot leg. The conditions achieved in the CCTF and SCTF 1arge break reflood f.ests j arc indicated on a j* graph along with the correlation of UPTF resdits in l Figure 18. The steam flow j

  • associated with typical PWR reflood i

conditions is also shown on tEis graph. As. indicated on the graph, I counterflowing water during reflood would be expected in SCTF but not in { CCTF, i.e., consistent with observations. The CCTF/SCTF difference is i due to the height of the hot leg (full-scale _ in SCTF but not in CCTF). The figure shows the SCTF results, in this regard, are closer to PWR-l typical. 1s Figure 18 shows, counterflowing water would be expected in 4 both Westinghouse and CE P6R's. i 2 4 i 162

4 u._ om.e ree us.a u..o _ __.L .. a

DEiEU?ah"** "" ""'"

i ua u. i i % h::2! E P u-E u- \\- ~ u-I b"MM="Y ""- ~- I I r?"c':::ct'.".t" u-l e an ins=== a====# usu u.-_ r . s.n 4 t e-l l 'a us s.u i,, W i i svaLuanon or arr Lee numaAon ouses LAnse ansAu tocA neptoon we ccw. sow Alep A PWR Basm ose LMF mot Lee Tas7 Result 5 1 nouns s \\ Conclusion l 2 The UTPF Downcomer separate Effects Test and Hot Leg S Test have provided useful information for evaluation of scaling both ects tests the direct results convey favorable and For conclusions t downcomer or, a.e., water penetrates to the reactor vessel encouraging hot Ing as well as or better than would be predicted from through a subscale results. For the downcomer situation, the present test data do i l not provide a broad enough base to evaluate the accuracy of sc i up from previous tests. The UPTF results presently available though, do g CCFL e suggest that j* sealing j from previous scales provioes at least a i conservative approach, and that approach will have to await upcoming UPTF test resultsdetermination o the UPTF data show that predictions from the largest In the hot leg, (Richter, et al at 1/13 scale based an area) are quite accurate subscale tests (*5 percent). The correlation which gives this successIul scaling is based on the j* parameter, i indicating approach. Application af the UPTF het leg results to US PWt's indic I that: (1) during $5LOCA reflux margin between condensation, large break LOCA reflood runbackactual flows and the (2) during as expected; and entrained in the hot legs. is likely for water de- \\ \\ - - - - - - ^ - - ~ ^ ^ ~ ^ ^ ~ f ^

l i i References 1.. Hofmann, K., " Status of the German UPTF Program," presented at the 13th Water Reactor Safety Information Meeting, October '22 - 25, 1985. 2.

Weiss, P.,

Sawitzki M. and Winkler, F. ; "UPTF, a Full-Scale PWR Loss-of-Coolant Accident Program," Atomkern-Energie Kerntechnik, Vol.49,1986. 3. Hertlein, R. and Weiss,.P.; "UPTF Experiment: PWR ECC Downcomer Countercurrent Flow Under Steam and Two-Phase Upflow Condition," presented at the October 26 - 29, 1987.15th Water Reactor Safety Information Meeting, 4. "1/5-Scale Countercurrent NUREG/CR-2106, November,1981. Flow Data Presentation and Discussion," 5. " Analysis of ECC Bypass Data,", NUREG-0573, July,1979. 6. " Application of Batte11e's Mechanistic Model to Lower Plenum Refill," NUREG/CR-2030 March.1981. 7. " Analysis of Flashing Transient Effects During Refill," NUREG/CR-1765, March,1981. 8. "Sunnary of Refill Effects Studies with Flashing and ECC Interactions," NUREG/CR-2058, November,1981. 9. Weiss, P. A. and Hertlein, R. J.; "UPTF Test Results - First 3 Separate Effects Tests," presented at.the 14th Water Reactor Safety Information Meeting, October 27 - 31, 1986. 10.

Richter, Horst J.;
Wallis, Graham B;
Carter, Kelly H.

and MJrphy, Stephen L.; "Deentrainment and Countercurrent Air-water Flow in Model PWR Hot Leg," Thayer School of Engineering, September,1978 11. Gardner, G. C., " Flooded Countercurrent Two-phase Flow in Horizontal Tubes and Channels," Int. J. Multiphase Flow, Vol. 9 No. 4,1983, pp. 367 through 382. 12. Wallis, G. B., " Flooding in Stratified Gas-liquid Flow," Dartmouth College Report No. 27327-9, August, 1970. EB

I 13. Ohnuki, A.. " Experimental Study of Countercurrent Two phas Horizontal Tube connected to Inclined Riser." Jo e Flow in 4 Science and Technology, March, 1986, pp. 219 througn zsz uclear i i 14. Krolewski, S. M., " Flooding Limits in a Simulat Hot Leg," Massachusetts Institute of Techaology, ed Nuclear reac of Requirement for a B.Sc. (1980). i Submission as Part i 15. " Experiment Data Report i Tests S-NC-28, S-NC-3, and SNC-48," NUREG/CR-2454for S Circulation Idaho, December 1981. , prepared by EG8G 1 16. " Experiment Data Report for Semiscale Mod-2A Natural Tests S-NC-5 and S-NC-6," NUREG/CR-2501, prepared b Circulation January 1982. 1 o, 17. Condensation " NUREG/CR-3654"PWt FLECHT-SEASET S Westinghouse, Electric Corpora, tion, August 1984.EPRI NP-3497, W e ux 18.

Mandl, R.

M., and Weiss, P. A., "PKL Tests on Energy Transfer i Mechanisms during Small-break No. 2. March-April 1982. LOCAs," Nuclear Safety, Vol. 23, ~ 19.

Thompson, S.

L., Kmetyk, L. N., "RELAP5 Assessment: PKL Natural i Circulation Tests," prepared by Sandia National Laboratories, i NURES/CR-3100. SAND 82-2902, January 1983. 20. Tasaka, K. et. al. Natural Ci*rculation, tests at"The Results of 5% Small-Break LOCA Tests an 1986, NUREG/CP-0082, Volume 4. Fourteenth Water Re , October 27-31, 4 k a i j i 1 1 i i J MS

Verification Analyses for Vold Fraction Prediction 1 i l i ] p i l}}

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